The risk of casualties from the uncontrolled re-entry of spacecraft and orbital stages

From the beginning of 2010 to the end of 2022, 951 intact objects (spacecraft and orbital stages) with a radar cross-section greater than one square meter re-entered the Earth's atmosphere uncontrolled. The total returned mass was about 1500 metric tons, with a mean of 116 metric tons per year, mostly concentrated (80%) in orbital stages. On average, objects with a mass greater than 500 kg re-entered every 8 days, those exceeding 2000 kg every 2 weeks, and those above 5000 kg around 3 times per year. Only 4% of the re-entries came from orbits with an eccentricity greater than 0.1, while 41% were from nearly circular orbits with eccentricity lower than 0.001. 52% of the re-entries occurred in the northern hemisphere and 48% in the southern one. The areas of the planet most affected where those between 30 deg and 60 deg north. However, excluding the polar regions, the re-entry flux per unit area was relatively uniform, from 60° south to 60° north, implying a ground casualty risk manly driven by the population density. 84% of orbital stages and 19% of spacecraft exceeded a casualty expectancy of 10-4, the ceiling recommended by several guidelines and standards worldwide. The total ground casualty expectancy over the 13 years analyzed was estimated to be 0.194, corresponding to a probability of injuring or killing at least one person of about 18%. After remaining relatively stable from 2010 to 2018, the casualty expectancy and probability have grown systematically from then on, leading in 2022 to a chance of casualty of 2.9%, with orbital stages and spacecraft contributing, respectively, 72% and 28%.